Oral History Transcript — Dr. Minoru Oda

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Interview with Dr. Minoru Oda
By David DeVorkin
In Baltimore, Maryland
August 5, 1988

Transcript

DeVorkin:

This is an interview with Dr. Minoru Oda, who is here at the IAU in Baltimore, and I understand you're recently retired from ISAS? OK, first of all, you've written recently some histories of Japanese astronomy, is that correct?

Oda:

Yes. Yes. There are two articles. One is on physics today. This is either December, '87 or January, '88. This was a special issue for PHYSICS IN JAPAN, and I wrote an article, what we learned from space. I think that was my title. And this is on Scan(?) Telescope. This again, either January '87 or December '86, so one year before, both of which, I wrote down the how in Japan space science in general, and particularly astronomy has a role. And I mentioned the whole institutional program in Japan, and also relationship between ISAS and other Japanese institutions for application of space. But I won't repeat this story now.

DeVorkin:

OK.

Oda:

And also I wrote a few more articles, more comprehensive things in Japanese, but it may not be useful for you.

DeVorkin:

Well, it may be useful if we can have them translated, possibly by —

Oda:

— by the Japanese —?

DeVorkin:

Yes, or possibly by my wife. She is Japanese.

Oda:

OK. Wonderful.

DeVorkin:

One thing you have not discussed in these, I imagine, is your own history, your own background, how you got into space work in the first place.

Oda:

All right. OK, then, let me tell my own history. It's kind of embarrassing, but — OK. At the last period of the wartime, I was a graduate student and also I was at the Naval Research Laboratory, and first my work was —

DeVorkin:

— you were at the Naval Research Laboratory?

Oda:

That's right, in Japan, OK, yes. And also I was a student, graduate student in the Osaka University physics department, and my career originally was nuclear physics. And then right at the end of the war, '43, I think, our nuclear laboratory north of university was studying the separation of Uranium -235, so my work was to help — my work as a student was to construct the very bright mass separator. This is so that there is a different story from wartime, I'm going to talk about, it is not interesting.

DeVorkin:

This is important because it's your training. I'm very interested in how people in nuclear physics, moving to cosmic ray physics, and then into astrophysics —

Oda:

— OK, then, I be rather in detail. The original idea of this mass separator came from Professor Myamoto in Tokyo University. We used to call it spiral orbit spectrometer, and it was a beta ray spectrometer, and I don't come into the detailed design of this

DeVorkin:

— no, that's all right.

Oda:

Then my professor at Osaka University thought that now this beta ray spectrometer is very — I mean, very, how you say, strong and bright, so that we could, we may be able to use this as, not mass spectrometer but mass separator. Then we started it, and naturally as a student the only thing I could do is to stop the leakage of the vacuum, and that kind of thing, that's all, I mean, not too intelligent work. But in the meantime, I made a calculation of the orbit of these particles in the spectrometer, and that was a time when the top of physics people, including Professor Nanaoka who you may not know, but who is very famous because he produced the theory or idea of Bohr's concept of nucleus and the electrons — he also having the concept of the nucleus at the center and the electrons. That was before the wartime.

DeVorkin:

Did he have that at the same time as Bohr?

Oda:

Hm mm.

DeVorkin:

I see.

Oda:

Totally independent. And this fact is known among a few physicists in this country too, but not very well known. But anyway, he was the boss of the physicists' community, and he and my professor, Professor Kecuchi, who produced the so-called Kecuchi line many years back, and —

DeVorkin:

The Kecuchi line?

Oda:

The Kecuchi line. And that again was simultaneous with G.P.T. Thompson and Davis and Germer, to verify that the electron is away. Anyway, so these top people decided that, after some work on the separation of uranium, they decided that perhaps uranium bomb, they used to call it uranium bomb, will not be achieved during this wartime, and in fact, in fact, to produce the atom bomb, you really needed the enormous amount of the power and industry and personnel of the United States, you see. Japan certainly could not have done that. So they —

DeVorkin:

— during the war.

Oda:

During the wartime.

DeVorkin:

Were you part of that? Were you aware of it?

Oda:

I was. I was helping them. I was not intelligent enough to judge whether it was possible or not possible or anything, because I was…

DeVorkin:

Were there arguments among different Japanese physicists, whether it was possible, during the war, or not?

Oda:

I don't think. I don't think — most of the physicists didn't believe that it could be done. So then what happened was that then all of this laboratory, nuclear laboratory in Osaka changed its subject to microwaves.

DeVorkin:

Well after the war?

Oda:

No.

DeVorkin:

Oh, during the war?

Oda:

During the war.

DeVorkin:

Oh, I see, when they decided they couldn't make the bomb.

Oda:

Yes. So we moved to Naval Research Laboratory of Japan.

DeVorkin:

And where was that?

Oda:

Oh, the main campus was in Tokyo. And this particular laboratory where I attended, I joined, was in Shizuoka Prefecture. The name of the city is Shimoda... So we worked there. No, there were two researches. One was the — in Tokyo, they had, and they made a study for the radar. The concept of radar was known, because a German informed us that there was a rather strange electronic instrument which was shot down at Rotterdam in Netherlands, and they sent this instrument or this design by submarine to Japan, so the Japanese knew of the existence of the radar. So Japanese Naval Research Laboratory quickly had been developing the radar.

DeVorkin:

So you moved from mass spectrometry and Uranium-235 separation into radar work.

Oda:

No, before that. So, in the Navy there were two currents of researches, with the microwaves. One was this radar, and what I joined was to develop the very large high powered magnetron. Apart from radar, independent of radar. The concept was that probably it could be used for — useful for radar and also it's almost a joke, but in Navy, they asked us scientists to develop the very, very high powered magnetron with which we could disturb the electrical system of the airplane or something.

DeVorkin:

Over what distance?

Oda:

Over 10,000 meters. Well, but that's — anyway, we didn't believe it. The scientists didn't believe it, but, so — again, I was a graduate student, so I helped my professor to do this work.

DeVorkin:

And your professor was?

Oda:

Okuchi. (?)

DeVorkin:

Kecuchi.

DeVorkin:

And he's associated with Watase. And in this institute, interesting thing is, Professor Yukawa and Tomonaga and those people who later became very big scientists in solid state theory of physics.

DeVorkin:

Yukawa was already very well known.

Oda:

Very well known, and Tomonaga was known among the scientists, and both of them were given the Nobel Prize later. And so this Naval Research Institute was a very peculiar place. It has these physicists, top class physicists, and a few students, including myself, only two or three, and we studied very hard, I mean, experimented very hard to produce high, hopefully output, but at that time high input power magnetron. So at the end of —

DeVorkin:

— what were your power sources? Your input power sources?

Oda:

Well, of course we had just —

DeVorkin:

Big step-up transformers?

Oda:

Yes. That's right. And at the end of the war, as a continuous wave output, we could radiate, how is that, radiate 10 kilowatts. 10 kilowatts ew is not negligible. Suppose you radiate 10 kilowatts of the wave here in this room, all of the metal things makes the nonpolar (?) discharge. It's very strong wave. But that's the maximum output. Now, the maximum input for which we invented totally new type of magnetron, rather than the cavity magnetron, total input then was 100 kilowatts ew. Output was very poor. Everything, she was not very high. Now, here again, it is not known in this country that magnetron, cavity magnetron, was originally invented in Osaka University many years before the end of the war, even before the war.

DeVorkin:

Before the British?

Oda:

Before the British, oh yes. Well, British are magnetron and the radar. That comes in something early forties. And the first invention was in thirties in Japan. But people didn't know that.

DeVorkin:

What were they developed for?

Oda:

Just technological interest of the engineering professor for electricity.

DeVorkin:

Who was it, do you know?

Oda:

Okabe. Professor Okabe. K. Okabe of Osaka University. And these people and the Professor Tomonaga and Kotaya, (?) those people who produced the theory of magnetron, has been awarded the Emperor's Prize even before the war. And people know that Professor Tomonaga, they assume he has been awarded the Emperor's Prize because of military part, but not that, it was awarded by magnetron. So anyway, OK.

DeVorkin:

Very interesting. OK.

Oda:

OK, so then after the war, then we didn't know what to do, and —

DeVorkin:

Were you affected at all by the results of the war, and the American occupation and interrogations?

Oda:

Well, my professor was interviewed by the occupation forces, the officer of the occupation force, and I think all documents' and papers and that sort of thing were taken away.

DeVorkin:

Were people interviewed about the nuclear work mainly?

Oda:

No, radio.

DeVorkin:

Radio.

Oda:

Radar. And I think this study of the magnetron was published somewhere in this country, in documents. I remember I saw it somewhere once. It exists.

DeVorkin:

OK. Now, I have to ask you about Hiroshima, if you don't mind. You had made the decision, or at least your senior physicists had made the decision that you could not have produced an atomic weapon during the war, and yet you saw it in the most awful way. Was this a — I know it sounds so simple and superficial to say, was this a surprise? But did it make people think that maybe they could have done it after all?

Oda:

In Japan?

DeVorkin:

Yes.

Oda:

No. No, among scientists, no. We thought that our resources were too poor, and the number of people who could be devoted to this study was too few. So long before, well, not too long, but some time before the end of the war, the physicists were considering that we'll lose this war anyway. We would lose this war anyway.

DeVorkin:

Without the atomic weapon.

Oda:

Without the atomic weapon, that's right.

DeVorkin:

Was there any sense that the Americans were building one?

Oda:

Well, I — even if Americans didn't build the atomic bomb, still physicists believed that we couldn't win. But I assume that if there were no atomic bomb, then there would be the battle in the main islands of Japan. That would be a disaster.

DeVorkin:

But the feeling still is — what did the non-scientists feel? Did they ask you, did they ask scientists, why didn't you build one of these things? Did they understand?

Oda:

Well, no. I mean, the public, average people did not believe in the quality or capability of Japanese physicists by that time.

DeVorkin:

Then.

Oda:

Then. Right. Only physicists knew that Kecuchi had discovered this electron being the wave, and there are many new discoveries, but — well, as a whole, I mean, there is no comparison to the whole integrated power, I mean intelligent power of the United States, or Europeans. So now then, immediately after the Hiroshima, we knew that this was the atomic bomb. And then we knew that — OK, then, soon the war will end. And there was a prince who was the younger brother of our emperor, who was the high official in the Navy, naval officer, and one time my professor asked him a question, he was a kind of patron to this magnetron laboratory, then the question was, do you really believe that we could destroy, could even shoot down the B-29 airplane, and then he simply laughed, "Suppose your professors," —

DeVorkin:

Your professor laughed?

Oda:

No, no, the prince laughed.

DeVorkin:

Oh, the prince laughed.

Oda:

And he said, rather openly among many professors surrounding him — and he – but this is a story which I heard, I was only a graduate student. And then he said that, "Well, suppose you go back to your industries in Tokyo and Osaka. Already due to the air raids, you can't do many researches, research work. But here the Navy protects you, so whatever you do, you do whatever you like." That was the philosophy of this prince. But I don't know, but I'm sure he pretended to the Navy itself that they were working hard to produce these techniques. He very recently died. He was a very liberal and a very nice officer.

DeVorkin:

There was one younger brother to Hirohito.

Oda:

There are three. Next was a very nice mountain climber, but he died.

DeVorkin:

That's the one, yes.

Oda:

And the second was this naval officer. And the third one is an archeologist who is still active.

DeVorkin:

My wife's grandfather went up the Matterhorn or Mt. Blanc with the second brother. So I didn't know (crosswalk) — he was his guide, many years ago.

Oda:

I see. Is that so? Incidentally, this prince who died earlier is the number 1 honorary member of the Japan Alpine Club. And I and my wife are the number 4000th regular member. Then, after the war, then I tried to join Professor Nishina's laboratory.

DeVorkin:

Yes, of the Klein-Nishina —

Oda:

That's right. And Nishina has established a laboratory in the Institute of Physical and Chemical Research, which I now direct after my retirement from the Space Institute.

DeVorkin:

I see. So this must not be government.

Oda:

This is semi-government, money from the government but separate.

DeVorkin:

So the mandatory retirement age does not apply to you as a director or ?

Oda:

Well, I'm the president of this institute and there is no age. It's decided by the term of service. Now, — well, anyway, so Professor Nishina wanted me and also Professor Watase to come to work on his own cyclotron after the war. But after the war, really everything was so much damaged, and also we were literally starving, so there is no point of doing physics. But we dreamed to do physics.

DeVorkin:

Did you meet in formal seminars?

Oda:

Yes. Yes, reading Heisenberg, Pauli's paper and so forth.

DeVorkin:

How did you get these papers? Were the libraries intact?

Oda:

Well, the PHYSICAL REVIEW and those magazines came to the occupation forces.

DeVorkin:

The PHYSICAL REVIEW.

Oda:

Yes. And I think that's the only, maybe two or three issues came to Japan, only at the library of the occupation forces.

DeVorkin:

And you could gain access?

Oda:

Yes, with permission. We could read it but certainly there were no copying machines there. We really had to read and memorize.

DeVorkin:

Could you write notes and take them home?

Oda:

Yes, that we could do. And then — but before we were appointed to Nishina's, the cyclotron was destroyed and thrown away. Occupation force destroyed it, and threw it in the Tokyo Bay.

DeVorkin:

Oda:

DeVorkin:

So these were MacArthur's occupation forces. But if the library was getting the PHYSICAL REVIEW, there must have been someone there who appreciated this. Has this been discussed later?

Oda:

Well, actually, after this event of throwing away the cyclotron — also another cyclotron in Osaka University, where I studied as a student, was also destroyed and thrown out, thrown away. And perhaps because of this, Dr. Lawrence and many, many American physicists were worried, and they sent a scientist as a rather high official to the headquarters whose name I'm trying to recall.

DeVorkin:

That's OK, we can find it.

Oda:

In a few minutes I might, he was so famous, and we are really obliged to him, and actually, after he, he's from Durham, Duke University. One time he was president or vice president of Duke University when he was still young. And because of this, after he's dead, his bones were buried in the same place as Professor Nishina's tomb. Well, anyway, so —

DeVorkin:

So they brought him over, and what was his job then to do?

Oda:

Then he helped to build the science council of Japan in Japanese economy and also he, well, essentially he really protected the scientists from the occupation forces.

DeVorkin:

Was there any kind of national organization for science before the war in Japan?

Oda:

Yes.

DeVorkin:

But that was not reconstructed? This was something new?

Oda:

This was something new, and more democratic.

DeVorkin:

I see. OK.

Oda:

So we call it, it's the Diet of the Scientists.

DeVorkin:

Were you in this in the beginning?

Oda:

No, I was too young. Well, actually I was sitting in one of the subcommittees for nuclear physics, as a graduate student. Already I was assistant professor or something. And then, then what happened was, well, then there's no way to study nuclear physics anymore, so I decided to continue my study, continue to study a kind of puzzle which I have had for the naval research, and that was the noise of the magnetron. And the noise of the magnetron, well, I mean, when we were doing research very quick, you might ignore, but I have been, this had been puzzling me all the time. So after the war, then I decided, actually I stole a couple of magnetrons which had to be all gone, I mean all given to the occupation force.

DeVorkin:

So they took away all the equipment from the Naval Research Laboratory also. OK.

Oda:

Yes. Yes. But actually, I stole two or three of the magnetrons with me.

DeVorkin:

How could you steal them? I mean, was the security not too strict?

Oda:

That's right. And there is no reason why they scare about the research and so forth. So then I went back to Osaka University, as a research associate then, and I did some research work on the noise of the magnetron. Later I found that a similar kind of research has been done at the Radiation Lab at MIT under, I forget the name. That Radiation Lab still exists as Building 20 of MIT, with the old, old blackboard. And then, I thought I understood something about noise of the magnetron, which was a kind of plasma oscillation.

DeVorkin:

Plasma oscillation. All right.

Oda:

Well, I didn't know the wording of the plasma oscillation or anything, but what I observed was understood as a plasma oscillation later. Now, then, I had heard a rumor that the sun is radiating the radio.

DeVorkin:

You had not read any of the British literature?

Oda:

No.

DeVorkin:

Were you still getting PHYSICAL REVIEW? Was that available?

Oda:

But you see, to go to Tokyo by train, you needed the ten hours or twelve hours of the train ride, you see, and besides you needed permission to do it, because the train was so full. So we might go to Tokyo, oh, once every two or three months, to read PHYSICAL REVIEW or IRE TRANSACTION and so forth, but, and in one day or two days, you cannot read all of them.

DeVorkin:

It was available in Tokyo, not in Osaka.

Oda:

No, not in Osaka. No.

DeVorkin:

OK.

Oda:

Well, then I thought —

DeVorkin:

— let me just ask at this point, sorry to interrupt, clearly there were still terrible problems with food and were there also with housing?

Oda:

Yes.

DeVorkin:

What was your life like, and did you have a family at this time?

Oda:

No. My parents were in Taiwan. My father was a medical doctor, and he was asked by Chiang Kai-chek to continue his teaching and practice in Taiwan. So we didn't hear too often from my parents. And my younger brother was the student that was taken, drafted to the Navy, and he was trained as a pilot, but fortunately he became teacher, leading, teaching stuff of kamikaze, so he himself survived. And he came back, oh, half a year after the end of the war, and re-entered the University of Tokyo.

DeVorkin:

OK. Did the university open right after the war?

Oda:

Has been always open, although the activity could have been orders of magnitude low, because we had to live, we had no house or many of the students and many of the professors had to live in the university, in the rooms, in offices and so forth.

DeVorkin:

Were you married at the time?

Oda:

No, no.

DeVorkin:

OK.

Oda:

And then my brother came back and he entered the university again. He's a lawyer. But in Tokyo really you have to worry about starving. But at that time I lived in Shizuoka Prefecture still. There, it's easier to get some potato or rice and so forth. And I remember that several times I carried food for my brother. Incidentally, now, then, afterwards, now he became a judge at the International Court at Hague right now.

DeVorkin:

At The Hague.

Oda:

Hague, yes.

DeVorkin:

OK.

Oda:

So, he was lucky not to go to kamikaze.

DeVorkin:

That made him a good judge.

Oda:

Yes.

DeVorkin:

Sorry, shall we go back to the magnetron work?

Oda:

That's right. And then I heard a rumor that the sun is radiating a noisy radio wave, so I thought that

DeVorkin:

— please tell me, can you remember how you heard that rumor?

Oda:

I don't remember.

DeVorkin:

Not from an American or another Japanese colleague? OK.

Oda:

At that time I had no friends in the United States. So somehow, some rumor was going around, maybe from the Navy, because let's see, the naval attack corps used to attack putting the sun behind, because then the radar could be disturbed, the radio wave by the sun, so pilots knew this by experience, or something like that.

DeVorkin:

OK, yes.

Oda:

So I constructed Japan's first radio telescope. By hand. So I couldn't afford the gadgets to do the parabola, so I rolled the tin plate, actually copper plate, to make a horn.

DeVorkin:

It was a horn. All right.

Oda:

And there was only one aircraft carrier which did not sink during the wartime, and I got as a war surplus the radar machine.

DeVorkin:

A complete radar unit?

Oda:

Yes.

DeVorkin:

OK.

Oda:

And then I got that receiver, and I changed, I mean, I devised the electronics. You see, for radar you need a very narrow band amplifier, but for receiving the noise you need a very wide band receiver. It took about half a year to realize, to organize this difference. But finally we got it, and we —

DeVorkin:

Can I ask you if you purchased the radar set from the aircraft carrier world surplus, did it still cost you money?

Oda:

No.

DeVorkin:

Oh, it did not cost you money, OK. Were you getting money at all for your own salary and whatever at this time?

Oda:

Well, the Ministry of Education supports us.

DeVorkin:

OK.

Oda:

Little, very little, but —

DeVorkin:

But there was no complete change as MacArthur came in?

Oda:

No. No.

DeVorkin:

The Ministry of Education existed before and continued.

Oda:

That's right. Well, but MacArthur's office, I mean, government had changed very, very drastic change, that was the educational system of Japan. Before then, the educational system was more the German system. Few universities, few high class students. But after the war, then it became many, many, many universities and many, many, many students. This is basic change. Now —

DeVorkin:

What about research? Did it support research more?

Oda:

No. Neither. I think they didn't care.

DeVorkin:

Did you have any feeling that they were trying to keep Japan from improving its physics or research?

Oda:

Oh. No, certainly they did not try to encourage or promote physics in Japan, particularly in nuclear science.

DeVorkin:

They wished not to encourage.

Oda:

Not to. That's right. And also, no research work for the engineering of aerodynamics? Or the airplane industry and so forth. It was all forbidden.

DeVorkin:

Aeronomy or aerodynamics?

Oda:

Aerodynamics.

DeVorkin:

Aerodynamics, yes, I understand, OK.

Oda:

And the whole thing was released when this, still I don't get this name of the man, came to the headquarters as science advisor. Then the whole thing changed.

DeVorkin:

Oh, he changed it?

Oda:

Yes.

DeVorkin:

OK, we must find out who he is. I'm sure it's well known. I just don't know, apologize.

Oda:

We scientists all feel very much obliged to him. And you remember, there are of course many, but particularly few Americans to whom Japanese are obliged, Japanese intellectuals are obliged. One is this. Another is Mr. Warner of the Boston Museum of Fine Arts.

DeVorkin:

Warner?

Oda:

Warner, I think, head of the department of Japanese arts, and we were told that he was the person who strongly suggested not to bomb Kyoto and (?). I think this is a true story. And there are a few other people who understood Japan, like Reischauer or Glue (?) or those people. Now, can I go back to the studies?

DeVorkin:

Sure.

Oda:

Then, so, I did some work on the solar radio astronomy, and then, but in the meantime —

DeVorkin:

What were you actually trying to do with solar radio astronomy?

Oda:

Well, just curious. I tried to receive the radio waves from the sun. And then one day, we found that it showed, the needle of the meter had gone to the extreme. So I thought that something was wrong. But it was indeed the so-called outburst of the solar radio wave, and —

DeVorkin:

Were you in contact with any observatories that were monitoring the sun? Were there any in Japan doing that at the time?

Oda:

Yes. OK. But that time, I knew that. Now I remember one name, Professor Hatanaka, who knew that there was radio astronomy growing, growing in Australia and in the United States. And now, then, the chronology is a little vague, but I'm not trained as an astronomer. Hatanaka is an astronomer. So often I asked him questions, what to do, what it would be valuable to do and so forth. And then I reported this discovery of the outburst to some committee, some meeting, and also Physical Society meeting and so on, but at that time, not yet with any foreign astronomers.

DeVorkin:

Was there a correlation with an optical outburst, a flare that was seen by the regular telescopes?

Oda:

Oh yes. Yes.

DeVorkin:

And this was new information?

Oda:

Well, new to me, but in the whole world, I think already the American astronomers or...

DeVorkin:

— the British?

Oda:

— the British must have known that.

DeVorkin:

What about the interest the Navy might have had in long range communication? Was there any interest on the part of the Navy in the flare work?

Oda:

No. So far as I remember, no.

DeVorkin:

There were no Navy people looking at what you were doing, to your knowledge?

Oda:

No.

DeVorkin:

OK…

Oda:

This is almost my own autobiography.

DeVorkin:

That's what I want. You get an idea of how I work.

Oda:

Yes. But I'm glad that you let me remind something which I wasn't too clear now. So it helps me. OK, then, by that time, my professor Watase — he's a very clever person, and he has a strategy, he has a philosophy. So his policy was, OK, now we cannot reproduce this cyclotron and we cannot do the nuclear physics, at least for the moment, with machines. So why don't we go in the direction of cosmic rays? So in this Watase Laboratory, he started to collect people. Some people came back from the war, and some new graduates of the university.

DeVorkin:

Can you give me some names?

Oda:

Those names of people? Oh yes. Let me write it down.

DeVorkin:

OK.

Oda:

Professor Oshio, this is last two — that's two years senior to me. And this is minus two, he's still professor to Osaka.

DeVorkin:

Higashi?

Oda:

Higashi. This one is retired, and Higashi is still active. And Kusumoto, this is minus two or so.

DeVorkin:

Kusumoto.

Oda:

Yes. Ozaki, that's retired. All in Osaka. There are many. Yes, there are many.

DeVorkin:

These are the principal ones along with you?

Oda:

Yes.

DeVorkin:

OK.

Oda:

And then, oh yes, I shouldn't forget — Miyaki, this is minus one. He became later the director of the Cosmic Ray Lab of the University of Tokyo. And he's now retired also. Now, these —

DeVorkin:

Are these all physicists?

Oda:

All physicists. And all of us were willing to use the cosmic ray as a machine, as an accelerator of particles, so we all were aimed towards the nuclear physics or particle physics.

DeVorkin:

Where was Yukawa at this time?

Oda:

Yukawa was in Kyoto.

DeVorkin:

OK. Were you in contact with him?

Oda:

Oh yes. And Yukawa, and particularly Tomonaga. More Tomonaga because Tomonaga was in the Navy for this radar research and good friend to Watase. So we often asked question to Tomonaga, what to do next and what we can do with the cosmic rays.

DeVorkin:

What did you decide to do with the cosmic rays? What did you want to study?

Oda:

Well, OK, before then, let me finish my radio.

DeVorkin:

OK, but before we do that, when was the switch? About what year are you talking about here?

Oda:

OK, now, 1945 r the end of the war. OK, '46, I did the noise r magnetron noise. And then '46, to say '47, '48, '49, I forget r solar radio. And it was not trivial to produce Japan's first radio telescope, you see.

DeVorkin:

No, I don't think so.

Oda:

And besides, at that time I came to the concept of the radio interferometer. But without knowing the Mills Cross or anything. But I needed a budget of 1,000,000 yen, but Professor Watase could not afford this for me. So I quit, and also by this time Professor Watase's policy was to construct the Cosmic Ray Laboratory, and during the period of establishing the Cosmic Ray Laboratory, he needed something, some research by which this laboratory could get a reputation.

DeVorkin:

So he was establishing the laboratory while you were still doing solar work. Was there any connection? Because Forbush and others were talking about the origin of cosmic rays in solar flares.

Oda:

No.

DeVorkin:

So there was no connection at all.

Oda:

No connection at all.

DeVorkin:

Did you ever think that cosmic rays might come from solar flares? I mean, were you interested in where they came from r or just how to use them as accelerators?

Oda:

As an accelerator.

DeVorkin:

As accelerators.

Oda:

You seer there are two big schools of cosmic rays.

DeVorkin:

Two big schools, OK.

Oda:

One is to use the cosmic ray as a sweep. As a probe of the solar, I mean the interplanetary space and electromagnetic nature of the space.

DeVorkin:

Right.

Oda:

And other is the origin of cosmic rays, and to use it as an accelerator. Now, this comes to astrophysics later.

DeVorkin:

That's the origins, right.

Oda:

Yes. And this goes to the high energy physics.

DeVorkin:

That's the accelerator.

Oda:

Right. Watase's intention was this.

DeVorkin:

The accelerator.

Oda:

The accelerator.

DeVorkin:

What about the probe over here?

Oda:

This has been done by Nishina Laboratory.

DeVorkin:

Yes, but isn't that also high energy physics, the probe of matter? It's not?

Oda:

No.

DeVorkin:

What is it? Nuclear physics maybe.

Oda:

Well, it's magnetohydrodynamics.

DeVorkin:

I see. OK.

Oda:

But the history is very interesting, because afterwards, I came to this category totally, you see.

DeVorkin:

To the origins.

Oda:

Yes.

DeVorkin:

But you weren't interested in it at that time. OK.

Oda:

And then, Watase urged me to work on solar radio, so that we can keep the reputation of the laboratory.

DeVorkin:

You're doing something. Right.

Oda:

Yes. And in the meantime, nuclear physics part would grow.

DeVorkin:

But in doing the solar radio, were you more interested in the sun and what it was doing and finding a way to monitor, or were you interested in the equipment and building the capability?

Oda:

In a sense, I'm an experimentalist, so I'm interested in the instrument. But of course once in a while, some new event coming up is of course exciting.

DeVorkin:

Now, in order to take advantage of that, did you have to read or talk to people or what?

Oda:

Well, sometimes there is no, very little communication, even in Japan, to travel to another city, as I said, was not too good.

DeVorkin:

So you were experimenting on your own.

Oda:

Yes. With my friends.

DeVorkin:

And how were you reporting this?

Oda:

OK, well, there are still the activities of the conferences and small conferences and colloquiums going on.

DeVorkin:

OK. So you continued working in radio.

Oda:

Yes. And then, in the meantime, from say 1947 to 1950 or something, Watase's lab has grown, the cosmic ray study, now at Mount Norikura mountain laboratory, Norikura.

DeVorkin:

So all of this was mountain-based? There were no balloon flights?

Oda:

Not yet. Not yet.

DeVorkin:

Not yet. Now, what kind of equipment did they have in cosmic rays, or will you talk about that when you get to the change?

Oda:

Yes. Now, then, — well, you see, there was this kind of psychology, that is, now there are many people, young people were coming to Watase's. Watase has a wonderful personality; so many people come to him. So now they are rebuilding their capability of doing some nuclear physics. And I was originally trying to do nuclear physics. So the psychology, to be alone, well, actually, I had one more friend, but to be alone with the solar radio, looking at now these nuclear physics activities going on, that is cosmic ray physics, I felt sort of lonely, so I changed my subject. So Watase strongly asked me not to do so, and go ahead with the radio astronomy, and he said I am the only one at the moment who can do the radio astronomy and radio astronomy could be great in the future. And he was right.

DeVorkin:

But you didn't feel that way.

Oda:

Yes. So I joined them.

DeVorkin:

He let you join them?

Oda:

Well, I asked him.

DeVorkin:

And he said?

Oda:

Well, he was sort of regretful.

DeVorkin:

But it was still all right. I see.

Oda:

He's a nice person. So I joined them. I essentially helped him to guide the whole group of young people.

DeVorkin:

Did he replace you at the radio project? Did somebody continue on?

Oda:

Oh yes. OK. I must say that, OK. Now, my radio place was replaced by Takakura, who later became the professor of Tokyo (?) Laboratory.

DeVorkin:

In radio.

Oda:

In radio.

DeVorkin:

Was this the beginning of radio astronomy in Japan, with you and then him?

Oda:

Well, before me, there was Hatanaka. He worked within the range of 200 megahertz. Now, this was the large antenna kind of thing. I have to be very fair about this now. All right, this radio astronomy was started by Hatanaka and the microwave, the 3000 megahertz, 10 centimeter, this is microwave, and the long wave radio astronomy has been done already, had been started by Hatanaka.

DeVorkin:

OK, and microwave 3000 megahertz —

Oda:

— megahertz and so forth was started by myself, and another history is, then from this group, from this group many new stars emerged, including Morimoto and

DeVorkin:

That's from Hatanaka's group.

Oda:

That's right. Morimoto and (?) is here. And this group has established the famous millimeter wave radio of? We called this Nobeyama Radio Laboratory. Incidentally, these stories are written by some article in SKY AND TELESCOPE also.

DeVorkin:

I think Woody Sullivan or other people may have written part of that. Yes, OK. We shouldn't get too far into the radio, now that you are moving into the cosmic rays. Now, when was that? That was '48, '49?

Oda:

'48, '49. Yes. Or even '50. Now, then what Watase and I did was to invite the top class of theoretical physicists to our group. Now Watase and I moved to Osaka City University.

DeVorkin:

Now, why did you make that move, going from Osaka University to the City University?

Oda:

OK. Also the City University offered order of magnitude larger budget to Watase. They believed in Watase and they asked Watase to make the Osaka City University to be high class university.

DeVorkin:

Build it up.

Oda:

That's right.

DeVorkin:

Where did they get their money, Osaka City University? Was it a public university?

Oda:

Municipal.

DeVorkin:

It's municipal.

Oda:

Yes.

DeVorkin:

Osaka University was for the prefecture or?

Oda:

Prefecture and city, yes, and very rich city, because many of the merchants, many of the industries gather around Osaka.

DeVorkin:

But these were obviously two universities that were in competition with one another.

Oda:

Yes.

DeVorkin:

Was this a usual situation?

Oda:

No.

DeVorkin:

But this was something that was too good to refuse.

Oda:

And then, what Watase wanted to do was to invite good top class theoretical physicists to the group; because we are doing experimental, we are doing the observatory; his philosophy is that this has to be backed by the good theory.

DeVorkin:

Now, his style was to use Cosmic Ray Physics Laboratory as an accelerator. What kinds of detectors did you have on the mountain, and who built them and what was your role?

Oda:

All right. We built Geiger-Mueller counter, Wilson cloud chamber, and Geiger-Mueller counter we originally made by our hands, by glassworks and so on. It's very hard work.

DeVorkin:

These were all shielded in various different ways?

Oda:

Yes.

DeVorkin:

And did you have any trouble getting the components, the machinery going?

Oda:

Well, we had to overcome many, many difficulties.

DeVorkin:

To calibrate it, did you need radioactive sources?

Oda:

Yes.

DeVorkin:

Did you have any trouble getting those?

Oda:

Well, we got those from the Isotope Society here in Japan, which is a society that was established by Nishina.

DeVorkin:

And was there any American intervention here? Did you have to register?

Oda:

No. I don't know. That part is the contact between the Isotope Society versus the GHQ in Headquarters. I don't know. Yes, I can imagine, there must have been something.

DeVorkin:

Was this very exciting for you?

Oda:

Oh yes.

DeVorkin:

What did you want to do?

Oda:

Well, I wanted to — now we know that there are meson showers and there are many things. So even, I decided to go not only to the mountain but to go underground. So we found an abandoned tunnel of railroad, railway, and we established, we built a laboratory, small laboratory, perhaps half, one quarter of this.

DeVorkin:

15 by 15 feet?

Oda:

Something like that, and putting the counters and so on and all the electronics, all done by ourselves, and —

DeVorkin:

Did you have unique designs for your counters, or did you follow the designs —?

Oda:

Well, OK, the counters, a very strange thing, all right, it's originally invented in Germany by Geiger, but it really needs various tricks. Tricks, yes. And sometimes it's better to purge the insides, sometimes better not to purge the insides, sometimes you put a little oil in it, it works better, but if some other person do this, then it doesn't work — all sorts of things.

DeVorkin:

Right. Now, how did you gain this experience, of knowing how to do it?

Oda:

By experience. And the one big event was that we invited Professor Nambu who has been professor, leading professor at Chicago University for oh, over 20, 30 years.

DeVorkin:

Chicago? Nambu?

Oda:

Yes. He's a very, very famous guy in this country. And also Hayakawa.

DeVorkin:

Is this when you first met Hayakawa?

Oda:

Yes. And Yamaguchi, and Nishijima.

DeVorkin:

Now, you invited them to be on the staff?

Oda:

Oh yes. Nambu was a professor. Hayakawa was an associate professor.
Yamaguchi and Nishijima were research associates. They were all young. And then, so, we all are very, very good friends to each other nowadays, I mean, with family and so on, except Nambu because Nambu is now in the States for 30 years, more than that.

DeVorkin:

He was in Chicago though during the war?

Oda:

No. No. After being with us, within a year or two years, all of them evaporate.

DeVorkin:

They all went on to other jobs. So Nambu is a Japanese who was in Japan —

Oda:

Yes, yes.

DeVorkin:

And he went to Chicago later.

Oda:

Well, he was invited to Princeton, Advanced Study, perhaps one year after this. And then Hayakawa went to MIT just for summer school and met Bruno Rossi. Here I start some part of the story which you asked.

DeVorkin:

OK. This is just marvelous.

Oda:

So Hayakawa met Rossi, and Rossi in 1952 —

DeVorkin:

Do you know why Hayakawa went to MIT?

Oda:

Well, there was just, there was a summer course or summer school. And any of the Japanese physicists wanted to go to United States to absorb something new or to make friends and so forth. We were really starting the information.

DeVorkin:

And Nambu wanted to do the same?

Oda:

Well, actually, he was. His work was very well known by that time. So, Institute Princeton Advanced Study actually invited him as a staff. And Yamaguchi also was invited by Illinois University, and Nishijima also to Illinois, and he became the prominent professor in Illinois for oh — 10, 15 years, and came back to Japan again, like me. And so I helped Watase to establish this experimental and theoretical group as a whole, so for a long time, for a few years, we called it the golden time, golden period of physics. Now, they were very able theorists.

DeVorkin:

And the money came from Osaka City University because they wanted to build up this department.

Oda:

Yes, the city itself.

DeVorkin:

The city itself.

Oda:

Even the governor was very, very anxious too.

DeVorkin:

Who do you feel, is there one person you can point your finger at and say he was responsible for this feeling of building up physics?

Oda:

OK. Well, there are two very able professors, Professor Kotake was an organic chemist, and Watase of course in physics, and there was the governor and vice-governor. I don't remember the names.

DeVorkin:

Of the prefecture?

Oda:

Yes.

DeVorkin:

OK.

Oda:

Of Osaka. They got an idea to make an Osaka MIT, because Osaka is an industrial city and there are many rich merchants and so forth, so they wanted to build an MIT there.

DeVorkin:

So the three of them got together and made that decision.

Oda:

Yes.

DeVorkin:

Ah, that's very good. OK.

Oda:

OK, then, all right, then 1951 or '52 —

DeVorkin:

Excuse me, with these three; do you know if there was any intervention by Americans coming in as advisors?

Oda:

No. Not anymore.

DeVorkin:

Not anymore. OK, I won't ask until you bring it up.

Oda:

And then Hayakawa, just as in summer course…

DeVorkin:

In '51 -'52, or summer of '51, it sounds like.

Oda:

Yes.

DeVorkin:

He traveled to MIT to study under Rossi, Bruno Rossi, OK. Did you know about Bruno Rossi at this time in Japan?

Oda:

Yes. Oh, Rossi is a great figure in cosmic ray physics. So in 1953 or '52 —

DeVorkin:

— you had all be using, I assume on the mountain where you were resuming your work on Nurikura, you were using coincidence circuitry?

Oda:

Yes, so-called.

DeVorkin:

And it was all electronic.

Oda:

Yes, so we use the Rossi circuit, Rossi's coincidence circuit.

DeVorkin:

Right. Was there anything where you modified it to make it better?

Oda:

Well, of course, in any experiment you — physicists try to change it, sometimes improve, sometimes make worse. So nothing could be identical.

DeVorkin:

Do you remember anything particularly that really helped or really destroyed the whole experiment? What was your worst decision?

Oda:

Well, I don't remember.

DeVorkin:

Do you remember your best decision?

Oda:

Yes.

DeVorkin:

What was that?

Oda:

Well, best would be too strong, was that in the underground, I thought I found a good way to detect the muon, and the muon itself is a very rare particle, and also, to detect the scattering of the muon, I kind of considered a new circuit or new technology. And then I thought that by this I could pick up the very, very rare event of the muon scattering, and I thought that I found it. And we wrote a paper, with my colleagues. And later, I found that —well, this could have been so, I mean, it could have been true, but I — and I noticed that I under-estimated the background count which comes from the radon, from some natural emanation, so then the discussion of the statistics of the scattering, very rare event, became kind of marginal. And by that time, I tried to do more other things, so that I stopped it.

DeVorkin:

OK, that's a nice aside. Now.

Oda:

OK, now, 1953, —

DeVorkin:

Well, Hayakawa is with Rossi. Are you in contact with Hayakawa during that time? Did you write letters?

Oda:

No, but I have been a friend of Hayakawa for years already.

DeVorkin:

Before 1951.

Oda:

Yes.

DeVorkin:

When did you first meet him?

Oda:

Well, the society is small in Japan, and we are about the same age, so in many society meetings and so forth.

DeVorkin:

So you knew him before he came to Osaka City University?

Oda:

Just barely knew, yes. And then Rossi wanted to construct a new cosmic ray air shower instrument. Under him was, of course there are many, many excellent physicists under him, but for this particular purpose, he had Bill Kraushaar who is in Wisconsin right now, and also George Clark, who were the just appointed young assistant professors, and Rossi needed one more who could work on the electronics or, well, experimental physics. And also Hayakawa knew that, at that time, anybody in Japan wanted to come to the United States whenever a chance arrived, so Hayakawa suggested — Hayakawa is a theoretical physicist. Hayakawa suggested my name to Bruno, who can, who could construct a radio telescope by hand and so forth, see.

DeVorkin:

That's why he thought you'd be good.

Oda:

And also I knew him quite well, as a good theorist, and so I got an invitation from Rossi to work together.

DeVorkin:

Sure, excellent.

Oda:

So I accepted, of course. And then, since then to '56, the three, somebody called the three of us as "Rossi's gang," three young — and we worked together. We found a place outside, quite far outside of Boston, like in Harvard. It's not that Harvard.

DeVorkin:

Oh, Harvard, Mass. is where the Oak Ridge station, Agassiz station is —

Oda:

—yes, that's right, Agassiz station. So we built in Agassiz station. And then after that, I think I might have that, oh yes, I have a good one, all right — I give this to you. Then, before, OK, this is — I give you a green book

DeVorkin:

yes, very nice —

Oda:

This is the biograph which I presented on my banquet lecture for the International Conference of the very, one to three, (?) in Tokyo, partly commemoration of my retirement.

DeVorkin:

This is February 3, 1988.

Oda:

Then this is the copy of biograph, and also I gave that green book to people.

DeVorkin:

Marvelous. Now, this is entitled "Background and History of Bamboo Screen."

Oda:

Yes. Bamboo Screen was named by Bruno Rossi.

DeVorkin:

Oh, that's right, as you say in the green book, OK, that's right.

Oda:

So what I said was that first, when X-ray, (?) X-ray was discovered by Bruno

DeVorkin:

— this is Bruno on the upper left?

Oda:

No, Bruno and Jaconi (?) and those people, he called theorists to MIT, and this is Geoff Burbidge.

DeVorkin:

Oh, Geoff, OK, all right. That's 1963.

Oda:

Yes, and Tommy Gold. And they shot out many theories, like in the galactic center the stars are crushing around and making X-rays. And then —

DeVorkin:

This is Sco-X-1?

Oda:

Well, then immediately after, Herb Friedman, still the strong X-ray, when the galactic center is under the horizon.

DeVorkin:

That's the galactic center. OK, yes, of course.

Oda:

So, it's not it. So I went to the Smithsonian Laboratory on Garden St. and then I pulled out lots and lots of Palomar Sky Maps.

DeVorkin:

Palomar Sky Survey Maps.

Oda:

That's right. And at that time, Bruno was away for half a year or so, three months or so, and Bruno let me use his office at MIT. So I put many sky maps on the wall, and looking for something strange near the Scorpio. And the key question was, whether it is diffuse or still. (?)

DeVorkin:

Now, this is after the first detection.

Oda:

Oh yes.

DeVorkin:

This is 1963.

Oda:

Yes. Here I have something —

DeVorkin:

— that's way out of order. You have a picture of the horn.

Oda:

That's right, this is it. That is 1948.

DeVorkin:

So, for the tape recorder, we'll get a copy of this, but this is a picture of the copper horn that you rolled with your magnetometer and the radar installation, the altazimuth radar. Which one are you here?

Oda:

Here.

DeVorkin:

So you're on the left here in profile. Who is with you?

Oda:

Takakura. Yes. I wrote the name down. And he succeeded me, and went to the laboratory later, as a radio astronomer, a real radio astronomer.

DeVorkin:

And this is your dream. This looks like not a Mills Cross but an interferometer.

Oda:

Yes. And one of our colleague astronomers, much later, much, much later, said that this is an unnecessarily complicated concept of the interferometer, so that it wouldn't have worked. OK, that's it. And then —

DeVorkin:

You're skipping over a page or two.

Oda:

And then, cosmic ray. Now, coming back to cosmic ray, so Agassiz —

DeVorkin:

So we're now in the 1950s again?

Oda:

Yes.

DeVorkin:

All right, go ahead.

Oda:

At Agassiz Bill Kraushaar and George Clark and myself worked hard to have the, to detect in "oods" ?) of Agassiz.

DeVorkin:

This is the big shower, air shower detector.

Oda:

Air shower detector.

DeVorkin:

What were the detectors? Were they Geiger counters again?

Oda:

That's what I was supposed to work on. That is a big scintillation counter. And by that time, the scintillation counter was the size of centimeter or one inch or something like that, and we wanted to be like one meter or something, very big thing, so I worked to produce the toluene and mixture of toluene and benzene —

DeVorkin:

What was the first material?

Oda:

Toluene. And other chemicals.

DeVorkin:

Benzene.

Oda:

Yes. And mixed with so-called wavelength shifter, because the radiation comes as an ultraviolet light, so wavelengths to be shifted, so that it fits to the photomultiplier.

DeVorkin:

Right. And these were what types of photomultiplier, 1-B-21?

Oda:

I forget about that.

DeVorkin:

That's standard.

Oda:

Yes. But very big ones.

DeVorkin:

That's pretty big, 1-B-21. aK.

Oda:

Ah, that's too small.

DeVorkin:

These were cathodes that were three or four inches in diameter.

Oda:

Exactly, yes. And now, in the original biograph you see here, its red flare, which means that —

DeVorkin:

It says "1954, MIT, Agassiz," and you have a red flare right under the Agassiz.

Oda:

Yes. It shows that after I left MIT, one night, one of those toluene detectors caught fire. You see, toluene over 1 meter diameter, can, when it fires, its enormous fire. So I heard that MIT was almost kicked out, kicked away from Harvard property. But I was not there. And I was (wasn't?) responsible to that. So since then George Clark and myself worked on making the big scintillation plastics, not a liquid. And then coming back to Tokyo, now, I was not back in Osaka but I was back in Institute for Nuclear Study of the University of Tokyo.

DeVorkin:

This is 1956.

Oda:

Yes.

DeVorkin:

Now, at this time you were still interested in what Watase's direction was, which was using cosmic rays as little accelerators.

Oda:

Yes.

DeVorkin:

Was there still an embargo on accelerators in Japan in 1956? Still you could not build accelerators in Japan?

Oda:

No. Wait a minute — no, that just about the time the accelerator was allowed to be constructed again. But already Watase and we were interested in cosmic rays, so we were going toward the direction of the cosmic ray. But now one thing which strongly influenced me was Bruno Rossi.

DeVorkin:

You of course now knew Rossi.

Oda:

That's right. Now, Rossi's concept of this large air shower instrument was to detect or to verify upper limit of the cosmic ray energy. His concept was, combined with Enrico Fermi's idea, that our galaxy has a magnetic field in it, and has a certain limited size, so that if the cosmic ray has to be stored in the galaxy, it should have some certain energy limit. And he calculated it to be like 10 to the 15th or 10 to the 16th electron volts.

DeVorkin:

We can't do it all today, but we can certainly get a start. So Bruno Rossi and Enrico Fermi had been thinking about the mechanism of storage on cosmic rays and what that mechanism might be.

Oda:

Yes. OK, let me be more precise. Enrico Fermi had a concept of magnetic field in the galaxy. Now, Bruno had a concept of the existence of upper limit in the cosmic ray, OK. So this was originally the experiment, the first experiment.

DeVorkin:

That was to try to detect the most energetic in the showers, OK. The total energy in the shower.

Oda:

Yes. And by that time, I came back to Tokyo to the Institute for Nuclear Study in Tokyo, and there I constructed this air shower array. Now, I had a dual purpose. One is along Bruno's line, the other was Watase's line, so in Tokyo, I made the whole instrument quite more complicated, in a sense complicated, because I added a tunnel, I dug a tunnel in the field, so that I could make a fairly large area muon detector, and also I had a spark chamber. At that time spark chamber was invented by my colleague Fukui, and —

DeVorkin:

By the way, now, you came back to Tokyo, but you left Osaka City.

Oda:

Yes.

DeVorkin:

Did you go for only a very specific amount of time; you knew you were going to come back? Did you know where you were going to go?

Oda:

Well, first, when I went to MIT, I knew that I would be coming back to
Osaka. And indeed, I went back to Osaka for three months. By that time, by that time the new institute, Institute for Nuclear Study was being established, while I was away. And Professor Watase wanted me to come to go to the newly established Institute for Nuclear Study.

DeVorkin:

He wanted you there.

Oda:

That's right, so I moved there, three months after I came back to Japan.

DeVorkin:

Did you want to move there yourself originally? Was it something you asked for?

Oda:

Neither. I mean, I was at MIT and I didn't know much about this new institute, and Watase suggested that it would be a much better place for me to work.

DeVorkin:

He didn't want you with him?

Oda:

Well, he said that now I'd better be independent from him. He's very nice person. He is the person, who never disturbed what his students are doing, and he always encouraged and he never disturbed. And that's how I learned my own philosophy for the young people. I have this feeling that physicists cannot be educated: they grow themselves. And the only thing teacher could do is not to disturb them. And that's Watase's philosophy.

DeVorkin:

Very nice. Very nice. So you're building this array that does two things.

Oda:

Right. And simultaneously at MIT, I was involved at the first concept. Now, John Lindsley, who succeeded me at MIT, tried to build a much, much larger air shower array in New Mexico, Albuquerque, so-called Volcano Ranch. It's something like 4 kilometer by 4 kilometer, very large place. And when I was there I could see even the rattlesnake. It's a very wild part of — so, this was going on. And also at Mt. Norikura we built the air shower array. And then finally, —

DeVorkin:

So you had one in Tokyo or outside of Tokyo —

Oda:

Yes.

DeVorkin:

One at Norikura —

Oda:

One at Norikura, and one in New Mexico. Agassiz is now closed, and then instead there was the one in Albuquerque.

DeVorkin:

Albuquerque, so this was a big world-wide array. Later on, I guess, you also —

Oda:

I'm coming to that. And then in parallel to this, this Rossi's idea attracted British and Australian people, so that they made their own big ones in Australia and in England, and also in Russia, and that strangely, Cosmic Ray Conference as being held once every two years, and they did say that every two years the upper limit of cosmic rays went up by one order of magnitude. So first, Bruno expected it to be 10 to the 16th, 10 to the 15th, or thereabouts, but in the meantime it went up to 10to the 17th and 10 to the 18th and even 10 to the 19th and 10 to the 20th now. Then the cosmic ray is not stored in the tiny little galactic reservoir. Now, then, in 1960, —

DeVorkin:

— knowing that, when did you realize that and how was that determined? What role did you play?

Oda:

Well, I was — essentially, the whole concept and idea was Bruno's, and I simply helped him.

DeVorkin:

But who first realized the storage —? Who was it?

Oda:

Oh. Well, it's quite natural. If you find something 10 to the 18th, if the spectrum goes beyond, you see, the spectrum was supposed to go like that, 10 to the 16th, and there is not log log. Now, the energy spectrum of cosmic ray goes a power law.

DeVorkin:

Power law, yes.

Oda:

It's very beautifully explained by Fermi. Now, Bruno's concept of it comes down like that somewhere. But now we have England, we have Australian, we have Japanese, we have American instruments, and then every cosmic ray conference and it goes like that, so —

DeVorkin:

Beyond that limit.

Oda:

Beyond that limit. 17th, 18th. So, then idea would be this, that somehow cosmic ray is not stored in the galaxy, that it comes all over the universe, no reservoir. Or there is something like that and there's two components. One component may be distributed all over the universe; the other is indivisible of the gallery.

DeVorkin:

— is stored, so a low energy and a high energy component blended together.

Oda:

Right. So there are two ways to study this. One is to make the structure of the spectrum as ? as possible, that's one way. And another way is look at the composition of the cosmic ray here, composition means proton and deuterium? And heavy, and compare this with this one, to see if the origin here and there.

DeVorkin:

So one is to look for this dip, a possible dip, at 10 to the 16th.

Oda:

Or kink.

DeVorkin:

Or kink, that's right. And the other is to compare the power laws in very different energy ranges. OK. I understand.

Oda:

Or composition.

DeVorkin:

The composition, sorry. Right.

Oda:

Now, 1957, this was another year, at least landmark for me. That is, in CERN in Geneva, by that time CERN had a cosmic ray group there. And Blackett from England —

DeVorkin:

P.M.S. Blackett.

Oda:

Yes, asked a question of CERN still should continue the cosmic ray work, or should quit it, namely, whether cosmic ray is still viable or useful for the high energy physics work. So here several people gathered, headed by, I forget his first name, he has passed away ten years ago, Newth, he is a student of Blackett's, and also Herb Bridge, he's the first student and good associate of Bruno. He's a second now to Bruno. Both of them, and say, ten to twenty people here, and I don't know what reason, but I was asked to be one of them.

DeVorkin:

This is at CERN.

Oda:

In 1957, yes.

DeVorkin:

Did you go?

Oda:

Yes. And I worked with them. And by that time, I had an idea that mu mesons come from the horizon more strongly than vertically.

DeVorkin:

Vertical, so the horizontal component is stronger.

Oda:

That's right. So that why don't we take advantage of the geography or geology or whatever of the Swiss to use a mountain as a filter for the mu meson, and do muon physics? Well, this is a little bit unfair, because I am mountain climber and like mountains. I utilized this three month or six month walking around and also considering physics. But the final answer was Blackett quit the cosmic ray, so there's no more cosmic ray physics at CERN.

DeVorkin:

So you were planning to do this, but then Blackett decided that there wouldn't be any.

Oda:

That's right.

DeVorkin:

So you didn't go to CERN at all?

Oda:

Oh no, I did go to CERN. And I discussed it with those people, what could be done and so forth, and whoever maybe head of the group, Newth or Bridge, wrote a final report to Blackett.

DeVorkin:

Oh, I see.

Oda:

And we worked for them, in (?) lectures. (?) indirectly?

DeVorkin:

I see, and he turned it down.

Oda:

I think so.

DeVorkin:

Had you severed your connections in Tokyo to go to CERN? Or did you have a leave of absence in Tokyo?

Oda:

Yes.

DeVorkin:

So you had something to go back to.

Oda:

Yes. Yes.

DeVorkin:

Or, did you think about staying at CERN?

Oda:

Yes, it was attractive idea, but, well, at that time I'd just got married, and we were expecting a baby, so there was good reason to go back to Tokyo.

DeVorkin:

OK.

Oda:

And then, then — I'm not quite sure. I give this to you, so I write down here. 1959, I think, Rossi got an idea to start a new astrophysics course at MIT. This was new.

DeVorkin:

This is a course. Does this include research? Or was it a teaching course?

Oda:

Teaching course. Yes. Well, research certainly; Rossi's group is a big group.

DeVorkin:

That's true.

Oda:

And Rossi's idea was, I think originally, he wanted to have Woltjier to come ...

DeVorkin:

Ludwig Woltjier.

Oda:

I think. This part, I need a confirmation. By that time, I was very much attached to Rossi, and we had many thoughts and so forth about — he told me that, but I have no way to confirm. Well, I can ask him, but, he had an idea to invite Woltjier, but Woltjier went to Columbia, and then I think Rossi thought that Rossi could use his students to do it, so Kraushaar and a theorist Olbert, he is still at MIT, Stanislav Olbert, Stan Olbert, and myself, these three, to give the course.

DeVorkin:

So you went from CERN then

Oda:

— CERN back to Tokyo, and then — so I thought it would be interesting, although astrophysics was still very new to me, but none of us were experts by that time.

DeVorkin:

Well, what kind of astrophysics was it? You were in cosmic ray physics. What did Bruno Rossi — did he write you a letter? What kind of communication was there?

Oda:

Well, Bruno was in Japan for a conference, and I think that was when he asked me if I'm interested in coming.

DeVorkin:

Did you tell him immediately?

Oda:

No. Perhaps I wrote back, I think. Now, then, because of the three — Kraushaar, Olbert, myself, and suppose you raise a flag of astrophysics, these three, physics in a different way.

DeVorkin:

What were you going to do? What did Rossi think you were going to do, first of all?

Oda:

I don't know. I think Kraushaar, Olbert and Oda will do something, and in fact, in fact, Kraushaar is very good intelligent person. He's an experimentalist and he's a perfect experimentalist. I really admire him as an experimentalist. Besides, he's very intelligent, so he talked about talked a lot about the synchrotron radiation, as a most important physical mechanism in astrophysics, and Albert talked lots about the plasma. By that time, Bruno and Albert had written a textbook on plasma physics. And I — I forget what I did, but anyway there were three major elements, and we put these three together.

DeVorkin:

You got there in 1959 then.

Oda:

No. All right. It's more complicated. Then this thing comes in.

DeVorkin:

This is still on your cosmic ray page.

Oda:

Yes.

DeVorkin:

Mt. Chacultaya?

Oda:

Yes.

DeVorkin:

And that is in Bolivia? OK.

Oda:

OK, then this story of my coming to MIT on the faculty was going on, and simultaneously, I got an idea that if we go very high altitude.

DeVorkin:

To put up one of the arrays, array shower detectors —

Oda:

Now, air shower is such a cloud of the particles which comes in.

DeVorkin:

As you've drawn it.

Oda:

Yes. Mostly electrons, muons, pions and protons and everything. But suppose if this origin for a primary, if, this is if primary is proton or other nuclear particle, then it is; but if this is a gamma ray, then what happens is that then you have only electrons and gamma rays, because this doesn't have pions and, if course, very rarely a gamma ray produced the other nuclear hadron particles, but that's very rare. But basically it should be electrons and 'gamma rays. So —

DeVorkin:

That's the nature of the shower, electrons and gamma rays.

Oda:

Yes. Right. So suppose at Mt. Chacultaya, you need to be very high, because you don't want the kind of contamination by —

DeVorkin:

You want to get as close to the different parts of the region where the secondary production is the greatest.

Oda:

Yes.

DeVorkin:

And that makes the shower as small as possible.

Oda:

Yes. And at this altitude, this is half an atmosphere pressure, exactly 15400 is one-half.

DeVorkin:

5200 meters.

Oda:

Meters. Very high. Very hard to work.

DeVorkin:

Quite high, yes.

Oda:

So Bruno called his good students. He called his good students and he announced that we now propose that, why don't we have a high mountain, very high mountain air shower array, to see if there is the gamma ray origin air shower exists or not? Namely, very high energy gamma ray exists or not? Then Ken Greisen of Cornell University — he was also the first student of Bruno — and we had a half a day meeting there, myself and also Ismael Escobar, who is the Spanish origin but he was head of the Andreas University at La Paz, Bolivia, and George Clark and who else, John Lindsley, and we discussed it, and then Greisen said, "Well, we can't be sure that if things will go as I said, but, it's worth to do." Then Bruno said, "OK, let's do that." That's how Chacultaya was started. And —

DeVorkin:

Where did the money come from for that? Was that from MIT?

Oda:

From MIT and also Air Force and also partly from University of Tokyo, maybe only 10 percent.

DeVorkin:

Oda:

DeVorkin:

Oh, so Tokyo University, the Institute donated manpower as well as a little bit of money.

Oda:

Yes. Yes. Money, too little, so lots of —

DeVorkin:

The money was too little.

Oda:

Yes, so that as Japanese usual, techniques.

DeVorkin:

Was support for cosmic ray physics getting any better at this time?

Oda:

Yes. Now, — how did this work, is that what the question was?

DeVorkin:

Was it easier to find the money?

Oda:

Yes.

DeVorkin:

It was. So through the fifties, things got better.

Oda:

Yes. Much better. Much better, yes.

DeVorkin:

Much better. Why did that change? How did it get better?

Oda:

Well, because the cosmic ray physicists work hard, and appealed to the publicity, to some extent.

DeVorkin:

Publicity?

Oda:

Yes. In Japan, at least.

DeVorkin:

And what did the publicity say? What was exciting?

Oda:

Well, by that time we know that there are many new particles. But I must confess that this experiment didn't produce as much as we expected.

DeVorkin:

On Chacultaya.

Oda:

Yes. And still, we are not sure, whether the very high energy gamma ray exists or not. Although the continuous observation here was useful to understand the air shower, the nature of the air shower, but it's not a basic science kind of thing. Well, so that while doing this, I was commuting between Chacultaya and Japan. On the way I dropped in here at MIT. And then…

DeVorkin:

Now, Chacultaya is in Bolivia.

Oda:

Yes.

DeVorkin:

So you go due north to MIT.

Oda:

Well, the only way to go there is using the Air Panagra. Does it still exist? Air Panagra? Combined Pan-American and Grace Airlines. We call it Panagra. It starts from New York via Miami to the south.

DeVorkin:

I see, so you end up going back to New York no matter what. That makes sense. Still, it's almost a polar route then to go back to Tokyo.

Oda:

Yes. OK, let me finish. Let me accelerate this. So then I had been already prepared for coming to MIT, and then one day, when we were at Cape Cod, we were walking —

DeVorkin:

We being?

Oda:

Cape Cod.

DeVorkin:

Who was "we"?

Oda:

Bruno and myself.

DeVorkin:

Were you working or on vacation?

Oda:

Walking. Very often, very often I stayed at his summer house, and actually my wife and my daughter who's coming this afternoon had a strong invitation to come to the summer house, but somehow they come here. And then he said, "There is something strange with the rocket observation."

DeVorkin:

Something strange.

Oda:

Strange. 1962. That is the famous first X-ray observation.

DeVorkin:

April 1962, something strange, this is after the observations.

Oda:

After the observations.

DeVorkin:

You are walking in the summer after April, the rocket has already gone.

Oda:

Yes, and he said that the sky, X-ray sky is very bright, and he doesn't know what it is. And by that time theorists had made a calculation saying that there is no physical process which could produce such strong X-rays from the sky.

DeVorkin:

Hard X-rays, soft X-rays?

Oda:

Either.

DeVorkin:

Either. Were you aware that he was interested in looking for X before? Or was this totally different? Rays?

Oda:

That's a key question. I did not know, but he somehow by his instincts or how you call it, he sensed, at least he sensed that it's worth to explore.

DeVorkin:

It's worth to?

Oda:

To explore. And then I asked him a question, much later, why you attempted — you see, he used the observation of X-ray from the moon as an excuse of getting these rocket flights.

DeVorkin:

Why did he feel he needed to use it as an excuse?

Oda:

Well, he couldn't verify of course and he couldn't tell a reasonable theory to expect the X-rays from the sky. But yet he somehow he sensed that it was to do.

DeVorkin:

Wasn't there some hint that there might be some non-solar X-rays from the idea of the synchrotron radiation?

Oda:

No. Stan Olbert and several theorists had done these calculations rather thoroughly. For example, could X-ray come from Crab Nebula? Or could come from some nebulosity or some stars or something else? And always answer was that it's 10,000 or 100,000 times too weak to be detected by a conventional counter. Yet Bruno was — felt something. So he needed the excuse to get — to look at the experiment— from NASA. So he and Martin Annis, AS and E, those people, I think used the detection X-ray from the moon to explore, to study the subject of the moon.

DeVorkin:

What evidence did they have that there were X-rays from the moon? Did they have evidence?

Oda:

No. No. But if the solar wind hits, solar X-ray hits the moon, then it could —and then, much later, I asked Bruno whether he really believes that X-rays come from the moon, and he said no. And then I still remember his famous sentence, he told me, was that, not precisely, but "Nature may be much more imaginative, or full of imagination, than human beings," or something like that. So I don't think he had believed.

DeVorkin:

Do you think that he knew about Herbert Friedman's work? That even though Herbert Friedman didn't do anything about it, that there was possibly some X-ray radiation in the galactic center?

Oda:

OK, look, Bruno didn't know that, at that time. And of course, everybody knew that Herb Friedman was working, had been working, was expert as a solar expert. But nobody knew that he was working on the celestial X- ray. That's the situation then. And then, we discussed, after the first experiment, and then I asked Bruno if he did the experiment, for a different season, because if this were geophysical events, then the different season, to do it for different seasons would make sense, and I'm sure that Riccardo Giacconi and Bruno already had planned this. And then they did it, and they found it, — well, that's the story. And then —

DeVorkin:

You were aware of all of this at the time?

Oda:

Yes. And...

DeVorkin:

You were back in Japan, though?

Oda:

Well, in 1962, summer of '62 I think I already knew that the second flight was done, I think.

DeVorkin:

That's right. There were two flights by the summer of '62. And you were on Cape Cod walking with Bruno.

Oda:

Yes. And then I carne here, March of '63. And then as I showed here, Tommy Gold and Geoff Burbidge —

DeVorkin:

— this is now on the first page of cartoons. (?) OK.

Oda:

Yes. And this is me, I'm too young looking.

DeVorkin:

You were then searching the Paloma plate vault.

Oda:

Yes.

DeVorkin:

Those materials, looking for an object?

Oda:

Looking for anything strange, anything diffuse, or anything?

DeVorkin:

How precise was the position? It wasn't that precise.

Oda:

Well, not precise. It was only one degree or two degrees.

DeVorkin:

Were you interested at all in improving the positional characteristics?

Oda:

Yes. And to do this, — well, the reason why I put this figure here was that I was —

DeVorkin:

— the picture of the horn —

Oda:

Yes. Subconsciously I was always interested in something theoretical, you see, including the size, something theoretical and so forth. So I carne to the concept of the rotating cage, by —

DeVorkin:

— it says, consciously to geometrical periodical structure.

Oda:

That's right. This is now only a story, but that's a joke. But, so, then I noticed that the rotating cage, if you look through the rotating cage, you see the moiré pattern moves. And then if the star, here, if the object here is compact, then you definitely see the moiré pattern, so that you see the flecks (?) from the object modulate.

DeVorkin:

Modulate, that's if the object's a point source.

Oda:

That's right. But if this is diffuse or larger than a certain size, then the flecks would not be modulated. So we decided to, well, actually I produced this instrument at MIT.

DeVorkin:

A rotating —

Oda:

Rotating cage, yes. Instead of a mouse, it has a tiny electric motor, preportional counter here.

DeVorkin:

Preportional counter where the eye is.

Oda:

Yes. Then, —

DeVorkin:

This was flown in an X-IS, is it?

Oda:

Well, then George Clark and myself discussed to use X-IS, and I went to NASA Headquarters. I met a person named App. The man who worked at NASA later is Al Opp, so this is a different App.

DeVorkin:

This is App. Do you know his first name?

Oda:

I forgot.

DeVorkin:

All right, so you went to NASA.

Oda:

Well, actually he's not as important as Opp later.

DeVorkin:

He's the first one you talked to.

Oda:

Yes. And then we decided to — well, actually, I think they were going to give us some space at the cockpit of the X-IS, and we are preparing the experiment, but then NASA changed its policy to fly X-IS not so high but to make it faster.

DeVorkin:

Why did they do that?

Oda:

I don't know. I mean their policy. And then at that time, we did not know that X-ray could be observed below 100 kilometer of altitude. And in fact, it can be observed, and George Clark himself flew balloons.

DeVorkin:

Is that a picture of Clark?

Oda:

Yes. He was much younger than this. And so, we thought, we can't do this. And then at that time

DeVorkin:

Was this your first contact with balloons, rockets, planes or anything like this?

Oda:

Rockets, yes. First time. And then Riccardo Giacconi in '64, he offered, he generously offered a little space, extra space in his rocket, which has been almost ready to go, so very quickly I worked by myself at the machine shop at MIT to produce the grid and bring it over.

DeVorkin:

Tell me a little more about how you decided to develop the grids. How did you get this idea of the rotating wheel?

Oda:

Well, first of all, the key question, the crucial question is that, the source is diffuse or point. Now, if you have a very narrow, very narrow slots or pinhole — I mean, the pipe, tubes — well, you may be able to define whether it is a point or it is diffuse, but to do that you have to point it precisely. So there must be some other way. Well, it's hard to tell you why I came to this concept of the rotating cage, but it's true that I saw a rotating cage by a squirrel or a mouse, and I think it was a mouse, on the streets of Brookline, Cleveland Circle or something.

DeVorkin:

Cleveland Circle?

Oda:

I think so. All of a sudden, I came to this concept.

DeVorkin:

You were machining these little tubes?

Oda:

The first one, yes.

DeVorkin:

And did they actually move or did you use the spin of the rocket?

Oda:

Oh, for this one, this one was rotating.

DeVorkin:

So you did have a little cage that rotated, so to speak.

Oda:

Yes. But this was not used, because the F-1S didn't go. And for the rocket, for the rocket, it needs a space, and the space which Riccardo gave me was a space very, very thing and flat.

DeVorkin:

Very narrow. So he was flying a flight and he let you fly with him.

Oda:

That's right. And even allowed me to use his counter. So only thing which I provided was simply these grids.

DeVorkin:

So what was he flying? Was he flying another experiment?

Oda:

Yes. I think to observe the energy spectrum of the Sco-X-l or something. I've forgotten.